1. Field of the Invention
This invention relates to a metal surface treatment composition containing an acrylic resin comprising a N-heterocyclic ring, treatment method and treated metal material, and in particular to a metal surface treatment composition containing an acrylic resin comprising a N-heterocyclic ring, treatment method and treated metal material giving improved corrosion resistance, film adhesion and slip properties (referred to also as "lubricity").
2. Description of Related Art
Conventionally, phosphate treatment, chromate treatment and non-chromate treatment, etc. were performed as surface treatments for food cans, car bodies, coil coatings for steel plate and metals for construction materials. For example, a phosphate film is formed on a metal surface as a pretreatment when organic coatings such as paints and adhesives are applied to metal surfaces such as iron, zinc, and aluminum. By subsequently applying an organic film such as a coating, corrosion resistance and film adhesion can be improved. However, conventional phosphate treatment did not necessarily provide sufficient corrosion resistance, film adhesion or slip properties to satisfy demand in recent years.
To improve corrosion resistance following phosphate treatment, it was common to apply a coating after first applying a primer coat. However, if a primer was first applied, although corrosion resistance and film adhesion improved, the number of coating steps increased, complicating the procedure and leading to higher cost.
"A Metal Surface Treatment for Composite Films" of Japanese Patent Laid-open publication No. Hei 5-117869 was proposed for example as a metal surface treatment which aims to omit the primer coating while giving highly developed corrosion resistance and film adhesion. The metal surface treatment of the aforesaid Japanese Patent Laid-open publication No. Hei 5-117869 is a phosphate surface treatment liquid comprising a cationic organic polymer compound or one of its salts having one or more cationic nitrogen atoms, and a molecular weight in the range of 1,000-1,000,000.
In the "Surface Treatment Method for Aluminum and Aluminum Alloys" described in Japanese Patent Laid-open publication No. Sho 51-73938, the metal to be treated is limited to aluminum. This method aims to confer corrosion resistance and film adhesion properties. It is described that this metal surface treatment method uses a liquid of which the principal components are water-soluble resins such as vinyl acetate, vinylidene chloride and acrylic acid or organic polymer film forming substances comprising emulsion resins, and a water-soluble titanium compound.
However, although they offer improved corrosion resistance and film adhesion compared with the prior art, neither the aforesaid metal surface treatment agent nor treatment method has reached recent demand requirements. In particular, in the manufacture of food cans using aluminum or its alloys, they do not prevent jamming, and in the coil coating of steel plate, lubricity is poor.